primate city (idea)

A city that is largest in a country, several times larger than the second-largest city. The rank-size rule predicts the population of a country's second, third, and smaller cities based upon the size of the largest city. The rule is logarithmic, but involves a coefficient that varies from country to country. The higher a country's coefficient, the higher the "primacy" of the largest city.

Most geographers would qualify the above definition: Not only must a primate city be far and away the largest city in a country, it must also dominate the country, economically and culturally. Some services will be found only in the primate city, so a primate city will usually be the capital of the country it is in. To put it another way, a primate city has the entire country as its hinterland.

It is not well understood why some countries have primate cities. It often seems related to economic underdevelopment of a country, and with a country's prior status as colony. However, the world's three largest countries in population (2002), China, India, and the United States, all have similarly-shaped rank-population profiles. The artificial nature of some national boundaries certainly plays a part: Many of these cities were the principal center of control for a particular colony of a Western power. Also, some primate cities may be a remnant of history: As a country goes therough the demographic transition, people leave rural areas, concentrating in cities. If a country had only one large city when this occurred, its primacy would be much higher than another country with a more even distribution of economic opportunity to begin with.